The rapid and extensive development of magnetic resonance imaging as a clinical diagnostic tool has brought about the need for specific pharmaceuticals designed to enhance image contrast between normal and diseased tissue. The major considerations for the design of MRI contrasting agents are high stability of the metal complex and high relaxivity of tissue derived water protons. Relaxivity is mediated by the number of waters coordinated to the imaging agent and the rate of exchanges of these waters with the bulk solution. Currently available MRI contrast agents suffer from a less than ideal contrast due to their relatively low relaxivity enhancement. A new class of MRI contrast agents with higher relaxivity can be prepared by simple modification of the existing Gd(TREN-Mc-3,2-HOPO)(H2O)2 complex. This proposal describes the synthesis of several monosubstituted TREN caps, the synthesis of a new derivative of the 3,2- HOPO chelating agent, and the combination of these two new units into ligands for gadolinium(III). The gadolinium complexes of these new ligands are promising candidates for new MRI contrast agents with enhanced relaxivity. These complexes are readily modified to effect in vivo targeting of the gadolinium complex to a specific biological site.